1. Field of the Invention
The present invention relates to a laser projector using an optical pumping valve.
2. Description of the Related Art
FIG. 1 shows the schematic structure of a three-dimensional video projector using a conventional liquid crystal light valve (LCLV). As shown in FIG. 1, a conventional three-dimensional video projector makes white light emitted from a high voltage metal-halide lamp 100 parallel by a collimating lens 200 and collects the parallel light at a liquid crystal display panel 300. The liquid crystal display panel 300 filters incident light according to a video signal and transmits the filtered light. The transmitted light is collected at an optical lens 400 and is projected to a screen 500. Accordingly, a video screen is obtained. However, the metal-halide light of a high voltage is used in the conventional three-dimensional video projector using a conventional liquid crystal optical valve. The light which is filtered by the liquid crystal display panel and is projected has a large dispersion angle and low brightness. Accordingly, an image focused on a screen has low contrast.
In general, there are two types of video projector using a CRT. One is a single tube type in which the picture of a projection tube is enlarged by transmitting the picture through a lens. The other is a three-tube type in which the respective pictures of red, green, and blue independent projection tubes are projected to a projection screen, thus combining the pictures in the projection screen. Accordingly, a color picture is obtained.
In the case of the three-tube video projector, as shown in FIG. 2, the red, green, and blue pictures irradiated from the respective projection tubes 110, 210, and 310 are combined in a projection screen 510 using an optical instrument 410. The projection tubes 110 and 310 on both sides of the central projection tube 210 for forming the red and blue pictures are fixed by a fixing means (not shown) at a predetermined angle.
The fixing means for fixing the projection tubes 110, 210, and 310 includes a housing member fixed to a setting unit (not shown) of a projector and a bracket (not shown) fixed to the housing member for fixing the projection tubes 110, 210, and 310.
The respective projection tubes 110, 210, and 310 control the convergence with respect to a projection screen by rotating the projection tubes 110 and 310 with respect to the central projection tube 210 at a predetermined angle. The focus lengths of the respective projection tubes are controlled by the driving circuit of the projector.
However, the projection tube assembly of the conventional projector constructed as above has a problem in that the space required for installation is relatively wide since the projection tubes 110, 210, and 310 are arranged more or less linearly and a lens unit is installed in each projection tube.
Also, since the distances between a projection screen 510 and the respective projection tubes 110, 210, and 310 are not uniform in the projection tube assembly, there is a difference in brightness among the pictures formed by the respective projection tubes 110, 210, and 310. Since there are no means for partially collecting light of the picture irradiated from the respective projection tubes to the edge of the screen, the resolution of the picture may be distorted at the edges of the screen.
To solve the above problem, it is an object of the present invention to provide a portable laser video projector using an optical pumping valve by which it is possible to improve the convergence characteristics and the white balance characteristics of the respective projection tubes, to improve the brightness and the contrast of a projection type display device, and to realize a laser image.
Accordingly, to achieve the above object, there is provided a laser video projector, comprising three optical pumping valves having central optical axes collected at one point, which are arranged to be separated from the point in which the central optical axes are collected by the same distance and a group of three projection lenses respectively installed in front of the three optical pumping valves, for projecting light from the three optical pumping valves.
In the present invention, each of the three optical pumping valves includes a laser resonator for resonating light of a certain wavelength, an optical pumping source for performing pumping so that the laser resonator can generate a laser beam, and an optical valve for filtering the laser beam emitted from the laser resonator so that the filtered laser beam forms a picture.
In the present invention, each of the three optical pumping valves comprises a laser resonator for resonating light of a certain wavelength, an optical pumping source for pumping the laser resonator so that it can emit the laser beam, a reflection type liquid crystal display panel installed to be parallel to the straight path of the laser beam in a place getting out of the way of the straight path as an optical valve for filtering the laser beam so that the filtered laser beam forms a picture, and a dichroic mirror installed on the straight path for reflecting the laser beam emitted from the laser resonator to the reflection type liquid crystal display panel and reflecting the laser beam filtered and reflected from the reflection type liquid crystal display panel to the straight path again.
Also, the laser resonator is preferably formed of a vertical cavity surface emitting laser (VCSEL) diode. In the VCSEL diode, an active layer is preferably formed of a single crystal layer of a Group II-VI or III-V compound semiconductor in the VCSEL diode or of a multi-quantum well layer or a superlattice layer by alternating contacts of different kinds of materials of a Group II-VI or II-V compound in the VCSEL diode. In the VCSEL diode, a mirror forming a cavity in the VCSEL diode is preferably formed of a dichroic mirror formed by the alternating contact of oxide dielectrics respectively having a high refractive index and a low refractive index or of a dispersion Bragg reflector formed the alternating contacts of a Group II-VI and II-V compound semiconductors respectively having a relatively high refractive index and a relatively low refractive index.
Also, the optical pumping source is preferably formed of a gas discharge tube in the pattern of a dot light source or a surface light source. The optical pumping valves are preferably an integrated type, the laser resonator and optical pumping source of which are in direct contact with each other, or a separated type, the laser resonator and the optical pumping source of which are separated.
In order to achieve the above object, there is provided a laser video projector using another optical pumping valve according to the present invention, comprising three optical pumping valves arranged linearly, mirrors installed in front of the two outer optical pumping valves and changing the light path of the outer optical pumping-valves, a color prism installed on the light path of the central optical pumping valve for reflecting the light reflected from the mirrors to proceed along the light path the same as the light path of the central optical pumping valve and directly transmitting the light irradiated from the central optical pumping valve, and at least one projection lens group installed in front of the color prism on the light path of the three optical pumping valves for projecting the light from the three optical pumping valves.
In the present invention, the three optical pumping valves each preferably comprises a laser resonator for resonating light of a certain wavelength, an optical pumping source for pumping the laser resonator so that it can emit a laser beam, and a transmission type liquid crystal display panel as an optical valve for filtering the laser beam so that the filtered laser beam can form a picture. Each of the three optical pumping valves comprises a laser resonator for resonating light of a certain wavelength, an optical pumping source for pumping the laser resonator so that it can emit the laser beam, a reflection type liquid crystal display panel installed to be parallel to a straight path of the laser beam at a location out of the way of the straight path as an optical valve for filtering the laser beam so that the filtered laser beam forms a picture, and a dichroic mirror installed on the straight path for reflecting the laser beam emitted from the laser resonator to the reflection type liquid crystal display panel and reflecting the laser beam filtered and reflected from the reflection type liquid crystal display panel to the straight path again.
Also, in the present invention, the laser resonator is preferably comprised of the VCSEL diode. An active layer is preferably formed of a single crystal layer of a Group II-VI and III-V compound semiconductor or of a multi-quantum well layer or a superlattice layer by alternating contacts of different kinds of materials of a Group II-VI or III-V compound in the VCSEL diode. A mirror forming a cavity in the VCSEL diode is preferably formed of a dichroic mirror formed by the alternation contact of oxide dielectrics respectively having a high relatively refractive index and a low relatively refractive index or of a distributed Bragg reflector formed of alternating contacts of Group II-VI and III-V compound semiconductors respectively having a relatively high refractive index and a relatively low refractive index.
Also, the optical pumping source is preferably comprised of a gas discharge tube in the pattern of a dot light source or a surface light source. In the optical pumping valves, the laser resonator and the optical pumping source are preferably in direct contact with each other or may be a separated type.
Also, in the present invention, the mirrors are preferably formed to be curved in order to prevent the image at the edges from being distorted.